An underwater wireless optical communications (UWOC) system using different non-return to zero (NRZ) modulation schemes is proposed. Dual X and Y polarized Laguerre-Gaussian (LG) modes {LG[0,3], LG[1,3]} are realized at 10Gbps data rate. It is found that the system using LG[1,3], offers 4.2m range by using non-chirped NRZ modulation at -21.7dBm receiver sensitivity and it can sustain 4.5m distance with 1.7mrad divergence, 0.1dB transmitter and 0.5dB receiver loss. Compared to existing UWOC systems, this design offers optimum performance with 8.2-9.5μm photodiode width, -11.47dB gain and -22.46dBm signal and -79.10dBm noise at receiver under clear and costal ocean scenarios.